SYMMETRY OF THE FLOWER 



125 



150. Symmetry of the flower. Most angiosperms have sym- 

 metrical flowers. The simplest are those whose parts are ar- 

 ranged as iii Figs. 122, 128, and 149, having radial symmetry. 1 



FIG. 126. Bilaterally symmetrical flower of sweet pea 

 A, side view; B, front view, dissected; s, standard; w, w, wings; k, keel 



A higher type of flower is that which shows bilateral symmetry? 

 as in Figs. 125 and 126. 



If the drawing of such a flower were folded along the axis of 

 symmetry, one half of the drawing would cover and correspond 

 with the other half. Some flowers are wholly 

 irregular, showing no sort of symmetry. 



151. The receptacle. The parts of the flower 

 are borne on a variously formed expansion 

 of the flower stalk known as the recepta- 

 cle. Usually, as in Fig. 122, this is only a 

 slight enlargement of the flower stalk, but 

 in the rose (Fig. 127), the pond lily (Fig. 137), 

 the magnolia, the Calycanthus, and a good 

 many other familiar flowers it is large and 

 conspicuous. 



FIG. 127. A rose 



Longitudinal section 

 After Decaisne 



1 Such flowers are also called actinomorphic, meaning ray-formed. 



2 These are called zygomorphic flowers (from Greek words signifying yoke 

 and/orm). In many floras these are described, as irregular flowers, 



